Reeling from a fierce security crackdown, the Muslim Brotherhood brought out mostly scattered, small crowds on Friday in its latest protests against Egypt's military coup.

While the remnants of the Brotherhood's leadership are still able to exhibit strong coordination from
underground, the arrests of thousands of its supporters and members - and the fear of more bloodshed - have weakened its ability to mobilise the streets.

The day's largest single Cairo demonstration was more than 10,000 people outside the presidential palace, with thousands also taking part in another similar-sized rally outside the capital.

However, the majority of protests on Friday were smaller than in the past, consisting of several hundred protesters or fewer around the country.

It was an intentional shift in tactics from a week ago, when the group failed to rally in a single location as a show of strength.

Security officials dubbed it the "butterfly plan" - a flurry of protests to distract them.

Rather than have protests converge in one square and encounter force from police and angry residents, the group appeared to purposely plan hundreds of small marches as another way of continuing demonstrations and avoiding bloodshed, according to security officials who spoke on condition of anonymity because they were not authorized to speak to media.

Protest organisers also tried a bit of subterfuge: They said a rally would take place in Sphinx Square in Cairo, but after security forces barricaded the site with barbed wire, tanks and roadblocks, only a few hundred people demonstrated nearby, and the biggest crowd converged across town at the presidential palace.

Tens of thousands heeded the Brotherhood's call nationwide for a day of "decisiveness", in which the group urged people to "break your fear, break the coup". They marched defiantly past tanks and armored vehicles on the streets of Cairo and other major cities.

More than 1,300 people, most of them Brotherhood supporters, have been killed since president Mohammed Morsi, a longtime leader in the group, was ousted in a popularly backed coup July 3.

Violence peaked two weeks ago when security forces attacked two Brotherhood-led sit-ins, killing more than 600 people in the assaults. More than 100 policemen and soldiers have been killed since the August 14 raids. Police stations, government buildings and churches also have been attacked.

"When it started, it was only about the return of Morsi to power," said 18-year-old protester Ahmed Osama, who says he lost friends in the recent violence and that his brother was shot. "Now it has gone past that. Blood has been shed."

He said that despite the arrest of Brotherhood leaders, "We are still here."

The Brotherhood has more than 80 years of experience operating secretly as a banned organisation. It was not until after the 2011 revolution that ousted president Hosni Mubarak that the group surfaced with its full might and created its own political party.

The group appears to have changed its tactics from two weeks ago, when it urged people to converge in a main Cairo square. Nearly 100 people died in that incident, with protesters jumping to their deaths off an overpass as residents and police fired on them from different vantage points.

They took cover in a nearby mosque, which the army besieged before arresting those inside.

In another development, US ambassador Anne Patterson left Egypt after a little more than two years at the post, the State Department said. David Satterfield will be acting ambassador, taking a temporary leave from post as director-general of the Sinai peacekeeping force, it added.

Patterson had come under criticism from both Morsi supporters and opponents, which each accused the US of supporting the other side in the political divide.

Cairo residents mostly stayed off the streets on Friday in anticipation of the Brotherhood rallies. A military-imposed nighttime curfew in Cairo and 13 other provinces started two hours earlier.

The location of the rally at the presidential palace was kept largely secret until the last hour, even from those leading the march. In expectation of possible protests converging there, security forces had blocked parts of the road in front of the presidential building, but had greater security around Sphinx Square.

One of the protest leaders, Ahmed Khaled, said organisers didn't tell demonstrators where the march was heading for security reasons.

Khaled and others said they were receiving instructions by phone on where to direct their march as it was happening. He declined to elaborate.

"We stopped communicating the itinerary and destination of the marches so nobody can follow us or wait for us with snipers at the arrival point," he said.

Thousands gathered in other cities, with smaller protests drawing hundreds and sometimes just dozens, including many women and children.

They marched through neighbourhoods that are largely sympathetic to them while others traveled outside their villages to areas where they are not known to avoid security forces and neighbors working with police in their hometowns.

Brotherhood officials in the provinces communicated with people in Cairo who alerted them to the overall plans, according to security officials and members of the group.

With little local media coverage of their protests, they also have activists stream live video of their rallies with cellphones. Videos are then disseminated on the group's Facebook pages and sent by email to foreign media outlets.

Notably absent were large numbers of supporters from the Brotherhood's more hard-line allies in the Salafi parties, which have begun distancing themselves from the group.

Those who did take to the streets chanted against the army chief, General Abdel-Fattah el-Sissi, who led the coup.

"The people want the death of the assassin!" the protesters yelled while waving the Egyptian flag and holding up yellow posters with the outline of a hand showing four fingers. Morsi supporters have used the symbol to remember the Cairo sit-in at the Rabaah al-Adawiya mosque, which in Arabic means "fourth."

The yellow poster was in every protest on Friday. According to members of the Brotherhood, who spoke on condition of anonymity because they feared reprisal, the posters are printed in secret locations, sometimes in the backs of Islamic bookstores and then distributed by youths in different towns.

A group, sometimes as small as three people, meets in private at night to discuss the form of protest, depending on the security situation that day. They then disperse to different mosques and relay the word to others through coded phone calls and text messages.

Imprisoned top leaders are also believed to be relaying messages through their lawyers to Brotherhood units that then pass the word on to other members. It is also common practice in Egypt for prisoners to bribe guards to use their phones.

Security officials say they have turned to retired police officers who worked for years tracking Islamist groups to help monitor the Brotherhood.

Security officials told The Associated Press they monitored former lawmaker Mohammed el-Beltagy for several days before arresting him on Thursday.

While largely peaceful, the protests saw some sporadic violence in Cairo and elsewhere as security forces fired tear gas at some marches and angry residents confronted Brotherhood supporters.

The group said seven people were killed nationwide; a government health official said only six died.

Also, a soldier was killed and three wounded at night when gunmen on a motorcycle opened fire at their post in the Suez Canal city of Port Said. Earlier, unidentified gunmen in two cars opened fire on a police station in Cairo, killing an officer and a civilian. The drive-by attack wounded another officer, according to the state-owned MENA news agency.

The Cabinet said the government, police, army and people were standing united "in the face of schemes against the unity and security of the nation."

"The terrorist groups and those breaking the law that want to tamper with the country's security will be blocked," the statement said, warning people to abide by the curfew.

Not all of Friday's protesters were from the Brotherhood. Some said they were seeking justice for relatives killed by security forces this month or protesting the way in which Morsi, Egypt's first freely elected president, was removed from power.

Tarek Safa, a 43-year-old engineer protesting with his teenage daughter in Cairo, said the Brotherhood may have lost its leadership but was not crushed.

"If we look at their 80 years of history, they have proven that they are stronger than the regimes. The leaders pass and they stay," he said. "They will not be defeated easily."